The subject matter disclosed herein relates to ceramic matrix composite (CMC) components and the joining of CMC subcomponents to form such components. More particularly, this invention is directed to a portion of a CMC nozzle and method of forming the CMC nozzle from multiple subcomponents utilizing one or more interlocking mechanical joints.
Gas turbine engines feature several components. Air enters the engine and passes through a compressor. The compressed air is routed through one or more combustors. Within a combustor are one or more nozzles that serve to introduce fuel into a stream of air passing through the combustor. The resulting fuel-air mixture is ignited in the combustor by igniters to generate hot, pressurized combustion gases in the range of about 1100° C. to 2000° C. This high energy airflow exiting the combustor is redirected by the first stage turbine nozzle to downstream high and low pressure turbine stages. The turbine section of the gas turbine engine contains a rotor shaft and one or more turbine stages, each having a turbine disk (or rotor) mounted or otherwise carried by the shaft and turbine blades mounted to and radially extending from the periphery of the disk. A turbine assembly typically generates rotating shaft power by expanding the high energy airflow produced by combustion of fuel-air mixture. Gas turbine buckets or blades generally have an airfoil shape designed to convert the thermal and kinetic energy of the flow path gases into mechanical rotation of the rotor. In these stages, the expanded hot gases exert forces upon turbine blades, thus providing additional rotational energy to, for example, drive a power-producing generator.
In advanced gas path (AGP) heat transfer design for gas turbine engines, the high temperature capability of CMCs make it an attractive material from which to fabricate arcuate components such as turbine blades, nozzles and shrouds. Within a turbine engine, a nozzle is comprised of a plurality of vanes, also referred to as blades or airfoils, with each vane, or a plurality of vanes, joined to a plurality of bands, also referred to as platforms.
A number of techniques have been used to manufacture turbine engine components such as the turbine blades, nozzles or shrouds using CMCs. CMC materials generally comprise a ceramic fiber reinforcement material embedded in a ceramic matrix material. The reinforcement material serves as the load-bearing constituent of the CMC in the event of a matrix crack; the ceramic matrix protects the reinforcement material, maintains the orientation of its fibers, and carries load in the absence of matrix cracks. Of particular interest to high-temperature applications, such as in a gas turbine engine, are silicon-based composites. Silicon carbide (SiC)-based CMC materials have been proposed as materials for certain components of gas turbine engines, such as the turbine blades, vanes, combustor liners, nozzles and shrouds. SiC fibers have been used as a reinforcement material for a variety of ceramic matrix materials, including SiC, C, and Al2O3. Various methods are known for fabricating SiC-based CMC components, including Silicomp, melt infiltration (MI), chemical vapor infiltration (CVI), and polymer infiltration and pyrolysis (PIP). In addition to non-oxide based CMCs such as SiC, there are oxide based CMCs. Though these fabrication techniques significantly differ from each other, each involves the fabrication and densification of a preform to produce a part through a process that includes the application of heat and/or pressure at various processing stages. In many instances, fabrication of complex composite components, such as fabrication of CMC gas turbine nozzles, involves forming fibers over small radii which may lead to challenges in manufacturability. More complex geometries may require complex tooling, complex compaction, etc.
Of particular concern herein are load bearing CMC components, such as turbine nozzle bands, with a focus on load path supports and retainment features of the CMC components, such as mounting supports on turbine nozzle band walls. These features typically require specific orientation of the fibers. More particularly, it is desirable to orient the fibers in the load bearing surfaces normal to the primary load path to provide an adequate wear interface. Some approaches to constructing these features may involve bending fibers around tight corners (e.g. small radii), which as previously stated, may lead to challenges in manufacturability.
Thus, an improved load bearing CMC component, such as a turbine nozzle band, and method of fabricating such load bearing CMC component is desired. The resulting load bearing CMC component, and more particularly, the included load path supports and retainment features, provide ease of manufacture, while maintaining strength and toughness of the overall CMC structure.